1. Field
The present invention relates to a device for laser-optical generation of mechanical waves for processing and/or examining a body.
2. Introduction
It is known from the prior art to excite mechanical waves and, in particular, ultrasonic waves in a body by laser light and to examine properties of the body by detection of these waves. For example, a detection laser beam is used to detect the mechanical waves and scans the surface of the body. The laser light of the detection laser beam is modulated by the mechanical waves and this modulation and hereby the mechanical waves thus can be detected interferometrically.
German Patent DE 196 41 653 describes a method for generating and detecting ultrasound in a material, this method being based on the above-described principle of excitation of mechanical waves and the detection thereof using a detection laser.
Various approaches are known from the prior art with regard to how the Gaussian beam profile of a laser beam can be suitably modified for excitation of mechanical waves in a body. U.S. Pat. No. 7,509,876 describes, for example, the use of a laser beam with an annular beam profile. Furthermore, a method in which a laser beam is modulated for the generation of ultrasound waves by a SLM (spatial light modulator) is disclosed in Tailoring Ultrasonic Beams with Optoacoustic Holography, by A. Meyer, S. Gspan, S. Bernet, M. Ritsche-Marte, in the Proceedings of the International Society for Optics and Photonics (SPIE), Volume 4969, 2003.
The devices known from the prior art for laser-optical generation of mechanical waves pose the drawback that the generation of suitable laser light intensity distributions for the excitation of mechanical waves is only possible for predetermined wavelengths and with limited accuracy.